International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 5
Number 4
December 2011
453
1 INTRODUCTION
In 1988, the Conference of Contracting Govern-
ments to the 1974 SOLAS Convention on the Global
Maritime Distress and Safety System (GMDSS)
adopted amendments to the 1974 SOLAS Conven-
tion concerning radiocommunications for the
GMDSS. These amendments entered into force on
1 February 1992. On 1 February 1999 the GMDSS
has become implemented for all SOLAS ships.
Since full implementation of the GMDSS some
changes both of regulatory and technical nature have
occurred.
The Maritime Safety Committee (MSC) at its
81st session decided to include, in the work pro-
grammes of the NAV and Radiocommunications
and Search and Rescue (COMSAR) Sub-
Committees, a high priority item on "Development
of an e-navigation strategy". One of the fundamental
elements of e-navigation will be a data communica-
tion network based on the some GMDSS infrastruc-
ture elements. It follows that question on moderniza-
tion of the GMDSS is legitimate.
2 THE ORIGINAL CONCEPT OF THE GMDSS
The original concept of the GMDSS is that search
and rescue authorities ashore, as well as shipping in
the immediate vicinity of the ship in distress, will be
rapidly alerted to a distress incident so they can as-
sist in a coordinated search and rescue operation
with the minimum delay. The system also provides
for urgency and safety communications and the
promulgation of maritime safety information (MSI)
(Czajkowski, 2000).
2.1 Functional requirements
The GMDSS lays down nine principal communica-
tions functions which all ships, while at sea, need to
be able to perform (IMO, 2004):
1 transmitting ship-to-shore distress alerts by at
least two separate and independent means, each
using a different radiocommunication service;
2 receiving shore-to-ship distress alerts;
3 transmitting and receiving ship-to-ship distress
alerts;
4 transmitting and receiving search and rescue co-
ordinating communication;
5 transmitting and receiving on-scene communica-
tion;
6 transmitting and receiving signals for locating;
7 transmitting and receiving maritime safety infor-
mation;
8 transmitting and receiving general radiocommu-
nication from shorebased radio systems or net-
works;
9 transmitting and receiving bridge-to-bridge com-
munication.
Yesterday, Today and Tomorrow of the GMDSS
K. Korcz
Gdynia Maritime University, Gdynia, Poland
ABSTRACT: Basing on a general concept, the main functions and the international requirements the Global
Maritime Distress and Safety System (GMDSS) have been presented. The modifications of the system since
its implementation and its current status have been described. The future of the GMDSS has been discussed as
well.
454
2.2 Radiocommunication services
The following radio services are provided for the
GMDSS:
a radiocommunication service utilizing geosta-
tionary satellites in the maritime mobile satellite
service (INMARSAT);
a radiocommunication service utilizing polar or-
biting satellites in the mobile satellite service
(COSPAS-SARSAT);
a radiocommunication service for transmitting
signals from survival craft stations in the 9200
9500 MHz band;
the maritime mobile service in the bands between
156 MHz and 174 MHz (VHF);
the maritime mobile service in the bands between
4,000 kHz and 27,500 kHz (HF);
the maritime mobile service in the bands 415 kHz
to 535 kHz and 1,605 kHz to 4,000 kHz (MF).
2.3 GMDSS Sea areas
Radiocommunication services incorporated in the
GMDSS system have individual limitations with re-
spect to the geographical coverage and services pro-
vided. The range of communication equipment car-
ried on board the ship is determined not by the size
of the ship but by the area in which it operates. Four
sea areas for communications within the GMDSS
have been specified by the IMO. These areas are
designated as follows (IMO, 2004):
Sea area A1 an area within the radiotelephone
coverage of at least one VHF coast station in
which continuous DSC alerting is available.
Sea area A2 an area, excluding sea area A1,
within the radiotelephone coverage of at least one
MF coast station in which continuous DSC alert-
ing is available.
Sea area A3 an area, excluding sea areas A1
and A2, within the coverage of an INMARSAT
geostationary satellite in which continuous alert-
ing is available.
Sea area A4 an area outside sea areas A1, A2
and A3 (the polar regions north and south of 75°
latitude, outside the INMARSAT satellite cover-
age area).
2.4 Equipment carriage requirements
Based on the range limitations of each radiocommu-
nication service the four sea areas have been defined
according to the coverage of VHF, MF, HF Coast
Radio Services and Inmarsat services. The type of
radio equipment required to be carried by a ship is
therefore determined by the sea areas through which
a ship travels on its voyage.
2.5 GMDSS equipment and systems
The following equipment and systems are provided
for the GMDSS (Fig. 1):
DSC - Digital Selective Calling;
INMARSAT Satellite System;
EPIRB - Emergency Position Indicating Radio-
Beacon (Inmarsat E, Cospas/Sarsat and VHF
DSC);
SARTs - Search And Rescue Transponders;
NAVTEX System;
NBDP - Narrow Band Direct Printing;
RTF - Radiotelephony;
DMC - Distress Message Control;
navigational equipment (for support).
Other elements of GMDSS to be showed in Fig.
1stand for as follows:
CES - INMARSAT Coast Earth Station;
SES - INMARSAT Ship Earth Station;
LUT - COSPAS/SARSAT Local User Terminal;
RCC - Rescue Coordination Centre.
CES
SES
EPIRB
VHF
HF
MF
NBDP
HF
MF
RTF
VHF
HF
MF
NAVIGAT.
EQUIPMENT
SARTs
NAVTEX
DMC
INMARSAT
COSPAS/
SARSAT
RCC
SAR
NBDP
DSC
RTF
NAVTEX
VHF
DSC
Figure 1. GMDSS equipment and systems (Korcz, 2007)
2.5.1 DSC specification
Digital selective calling (DSC) is designed for au-
tomatic station calling and distress alerting. Each
call consists of a packet of a digitized information.
DSC calls can be routed to all stations, to an indi-
vidual station or to a group of stations.
The system is used by ships and coast stations in
the MF, HF and VHF maritime communication
bands.
The system is a synchronous system using char-
acters composed from a ten bit error-detecting code.
The first seven bits are information bits. The last
three bits are used for error-detection. Each charac-
ter is sent twice but separated in time and a message
check character added at the end of the call.
455
Technical characteristics and operational proce-
dures for the use of DSC equipment are described in
the following documents:
Recommendation ITU-R M.493 ‘Digital selective
calling system for use in the Maritime Mobile
Service’.
Recommendation ITU-R M.541 ‘Operational
procedures for the use of digital selective-calling
(DSC) equipment in the Maritime Mobile Ser-
vice’.
2.5.2 Inmarsat specification
The original concept of the GMDSS includes
three Inmarsat services: A, B and C.
Inmarsat A provides two-way direct-dial phone
connection as well as fax, telex and data services at
rates between 9.6kbps up to 64kbps.
Inmarsat B was first maritime digital service,
launched in 1993, and remains a core service for the
maritime industry. It supports global voice, telex,
fax and data at speeds from 9.6kbps to 64kbps, as
well as GMDSS - compliant distress and safety
functions.
Inmarsat C is one of the most flexible mobile
satellite message communication systems, it has the
ability to handle commercial, operational and per-
sonal messages just as easily as distress and safety
communications.
It offers two-way, store-and-forward packet data
communication via a lightweight, low-cost terminal.
Inmarsat C is recommended for the any of the fol-
lowing applications:
E-mail and messaging
Fax and telex
SMS text
Remote monitoring
Tracking
Chart and weather updates
Maritime safety information
GMDSS
SafetyNET and FleetNET
2.5.3 NBDP specification
The Narrow Band Direct Printing NBDP (ra-
diotelex) systems employs error correction in the
form of ARQ (Automatic Retransmissions Request)
and FEC (Forward Error Correction). The technical
details of the error correction are defined by the
ITU-R in Recommendation M.476 and the Recom-
mendation M.625. Radiotelex is also known as Tel-
ex Over Radio (TOR).
2.5.4 NAVTEX specification
International NAVTEX (NAVigational TelEX)
service means the co-ordinated broadcast and auto-
matic reception on the frequency 518 kHz of mari-
time safety information (MSI) by means of Narrow
Band Direct Printing (NBDP-FEC) telegraphy. The
operational and technical characteristics of the
NAVTEX system are contained in Recommendation
ITU-R M.540. Performance standards for shipborne
narrow-band direct-printing equipment are laid
down in IMO Assembly resolution A.525(13).
The principal features of NAVTEX service are as
follows:
the service uses a single frequency (518 kHz) on
which coast stations transmit information in Eng-
lish on a time-sharing basis to prevent mutual in-
terference; all necessary information is contained
in each transmission;
the power of each coast station transmitter is reg-
ulated so as to avoid the possibility of interfer-
ence between coast stations; Navtex transmis-
sions provide a range of about 250 to 400 nautical
miles;
dedicated Navtex receivers are used on the board
of the ships; they have the ability to select mes-
sages to be printed, according to a technical code
(B1B2B3B4) which appears in the preamble of
each message.
3 LAST DECADE GMDSS MODIFICATION
The last decade modification of the GMDSS has
concerned both technical and regulatory issues.
3.1 Technical modification of GMDSS
The most important GMDSS modification has con-
cerned the Inmarsat. In 1999, Inmarsat became the
first intergovernmental organisation to transform in-
to a private company and, in 2005, was floated on
the London Stock Exchange. It caused that at present
Inmarsat is recognised as a leader in mobile satellite
communication field.
Inmarsat Fleet service provides both ocean-
going and coastal vessels with comprehensive voice,
fax and data communications. At present the Fleet
range of services includes:
Fleet 77
Fleet 55
Fleet 33
Inmarsat Fleet 77 has been introduced in 2002,
and Inmarsat Fleet 55 and 33 in 2003.
Inmarsat Fleet's high-quality Mobile ISDN and
cost-effective IP-based Mobile Packet Data Services
offer unparallel connectivity for access to e-mail and
the Internet, weather updates, video conferencing
and vessel monitoring systems.
Fleet 33 offers global voice as well as fax and a
choice of data communications at up to 9.6kbps.
456
Fleet 55 offers global voice and high-speed fax
and data services at up to 64kbps.
Fleet 77 is Inmarsat's most advanced maritime
service, providing global voice and high-speed fax
and data services at up to 128kbps. It fully supports
the GMDSS and includes advanced features such as
emergency call prioritization, as stipulated by IMO
Resolution A.1001 (25). Fleet F77 also helps meet
the requirements of the International Ship and Port
Facility Security (ISPS) code, which enables the
cost-effective transfer of electronic notices of arri-
val, crew lists, certificates and records.
Inmarsat Fleet series are recommended for the
applications showed in Table 1.
Table 1. Applications of Inmarsat Fleet series
__________________________________________________
Fleet 33 Fleet 55 Fleet 77
__________________________________________________
Data transfer + + +
Internet + + +
E-mail and messaging + + +
Fax + + +
SMS text + + +
Voice + + +
Crew calling + + +
Encryption - - +
Videoconferencing - - +
Remote monitoring + + +
Weather updates + + +
Telemedicine + + +
GMDSS functions - - +
__________________________________________________
Because Fleet 77 is IP compatible, it supports an
extensive range of commercially available off-the-
shelf software, as well as specialized maritime and
business applications. Fleet 77 also ensures cost-
effective communications by offering the choice of
Mobile ISDN or MPDS channels at speeds of up to
128kbps.
FleetBroadband is Inmarsat's next generation of
maritime services delivered via the Inmarsat-4 satel-
lites. It is commercially available since the second
half of 2007. The service is designed to provide the
way forward for cost-effective, high-speed data and
voice communications (Table 2).
Users have the choice of two products (FB250
and FB500). Both use stabilized, directional anten-
nas, which vary in size and weight. The above deck
antennas are smaller than other Fleet products.
Table 2. FleetBroadband performance capabilities
__________________________________________________
FB250 FB500
__________________________________________________
Data
Standard IP Up to 284kbps Up to 432kbps
Streaming IP 32, 64, 128kbps 32, 64, 128, 256kbps
ISDN 64kbps
Voice 4kbps and digital 3.1kHz audio
Fax Group 3 fax via 3.1kHz audio
SMS Standard 3G (up to 160 characters)
Antenna
Diameter from 25cm 57cm
Height from 28cm 68cm
Weight from 2.5kg 18kg
__________________________________________________
FleetBroadband supports an extensive range of
commercially available, off-the-shelf software, as
well as specialized user applications. It is ideal for:
Email and webmail
Real-time electronic chart and weather updates
Remote company intranet and internet access
Secure communications
Large file transfer
Crew communications
Vessel/engine telemetry
SMS and instant messaging
Videoconferencing
Store and forward video.
It should be also noted that Inmarsat E service
ceased to be supporting GMDSS in 2006 and In-
marsat A service – in 2007.
In the same time, instead of the Inmarsat E ser-
vice, the new Cospas-Sarsat Geostationary Search
and Rescue System (GEOSAR) has been introduced
as completion of the Low-altitude Earth Orbit Sys-
tem (LEOSAR). These two Cospas-Sarsat systems
(GEOSAR and LEOSAR) create the complementary
system assists search and rescue operations (SAR).
As the result of the hard work of International
Maritime Organization (IMO) other two new sys-
tems have been introduced:
Ship Security Alert System SSAS (in 2004),
Long-Range Identification and Tracking of ships
LRIT (in 2009).
Although the above mentioned systems are not a
part of the GMDSS, in the direct way they use its
communication means.
At the end it’s worth to note that the International
Cospas-Sarsat System has ceased satellite processing
of 121.5/243 MHz beacons on 1 February 2009 and
that on 1.01.2010 AIS-Search and Rescue Transmit-
ter (AIS-SART) have been introduced as well.
3.2 Regulatory modification of GMDSS
At a regulatory level a modification of the GMDSS
is coordinated by two international organizations:
International Maritime Organization (IMO) and In-
ternational Telecommunication Union (ITU).
IMO modifications are mainly concerning to the
amendments to Chapter IV of the International Con-
vention for the Safety of Life At Sea (SOLAS) and
to the IMO resolutions.
From the Radiocommunication point of view, the
most important modification was adoption by IMO
457
of Resolution A.1001(25) dated 29.11.2007 on Cri-
teria for the Provision of Mobile Satellite Communi-
cation Systems in the GMDSS and revision of Chap-
ter IV of IMO SOLAS Convention extends the
International Mobile Satellite Organization (IMSO)
oversight to GMDSS Services provided by any sat-
ellite operator which fits criteria.
ITU modifications are mainly concerning to the
amendments to Radio Regulations. These amend-
ments were adopted by two Word Radiocommunica-
tion Conferences (WRC).
The first World Radiocommunication Conference
took place in 2003 (WRC-03) and in the field of
maritime radiocommunication it took up following
main issues:
to consider Appendix 13 and Resolution 331
(Rev.WRC-97) with a view to their deletion and,
if appropriate, to consider related changes to
Chapter VII and other provisions of the Radio
Regulations, as necessary, taking into account the
continued transition to an introduction of the
Global Maritime Distress and Safety System
(GMDSS) (Agenda Item 1.9);
to consider the results of studies, and take neces-
sary actions, relating to exhaustion of the mari-
time mobile service identity numbering resource
(Resolution 344 (WRC-97)) (Agenda Item
1.10.1);
to consider the results of studies, and take neces-
sary actions, relating to shore-to-ship distress
communication priorities (Resolution 348
(WRC-97)) (Agenda Item 1.10.2);
to consider measures to address harmful interfer-
ence in the bands allocated to the maritime mo-
bile and aeronautical mobile (R) services, taking
into account Resolutions 207 (Rev.WRC-2000)
and 350 (WRC-2000), and to review the frequen-
cy and channel arrangements in the maritime MF
and HF bands concerning the use of new digital
technology, also taking into account Resolution
347 (WRC-97) (Agenda Item 1.14).
The second Word Radiocommunication Confer-
ence took place in 2007 (WRC-07) and the main
maritime radiocommunication items were as follows
(ITU, 2008):
taking into account Resolutions 729 (WRC-97),
351 (WRC-03) and 544 (WRC-03), to review the
allocations to all services in the HF bands be-
tween 4 MHz and 10 MHz, excluding those allo-
cations to services in the frequency range 7 000-
7 200 kHz and those bands whose allotment plans
are in Appendices 25, 26 and 27 and whose chan-
nelling arrangements are in Appendix 17, taking
account the impact of new modulation tech-
niques, adaptive control techniques and the spec-
trum requirements for HF broadcasting (Agenda
Item 1.13);
to review the operational procedures and re-
quirements of the Global Maritime Distress and
Safety System (GMDSS) and other related provi-
sions of the Radio Regulations, taking into ac-
count Resolutions 331 (Rev.WRC-03) and 342
(Rev.WRC-2000) and the continued transition to
the GMDSS, the experience since its introduc-
tion, and the needs of all classes of ships (Agenda
Item 1.14);
to consider the regulatory and operational provi-
sions for Maritime Mobile Service Identities
(MMSIs) for equipment other than shipborne
mobile equipment, taking into account Resolu-
tions 344 (Rev.WRC-03) and 353 (WRC-03)
(Agenda Item 1.16).
4 FUTURE OF GMDSS
In Author’s opinion, the future of the GMDSS is
closely connected with the development of the e-
navigation project and with a role of the GMDSS in
this process.
For realizing the full potential of e-navigation, the
following three fundamental elements should be in
place (Korcz, 2009):
1 Electronic Navigation Chart (ENC) coverage of
all navigational areas;
2 a robust electronic position-fixing system (with
redundancy); and
3 an agreed infrastructure of communications to
link ship and shore.
It is envisaged that a data communication net-
work will be one of the most important parts of the
e-navigation strategy plan.
In order to realize efficient and effective process
of data communication for e-navigation system, the
existing radio communication equipment on board
(GMDSS), as well as new radio communication sys-
tems should be recognized.
The above mentioned GMDSS MF, HF and VHF
equipment and systems (Fig. 1) can be also used as a
way of data communication for the e-navigation sys-
tem, provided that this equipment will be technically
improved by means of:
digitization of the analogue communication MF,
HF and VHF channels;
application of high-speed channel to GMDSS;
utilization of SDR (Software Defined Radio)
technology;
adaptation of IP (Internet Protocol) technology to
GMDSS;
integration of user interface of GMDSS equip-
ment; and
any other proper technology for GMDSS im-
provement.
458
This technical improvement of GMDSS equip-
ment may mean the potential replacement of the
conventional equipment by virtual one.
In this approach to development of e-navigation
it is very important that the integrity of GMDSS
must not be jeopardized.
With respect to the radiocommunication aspects
required for e-navigation (modernization process),
the following should be taken into account as well :
autonomous acquisition and mode switching;
common messaging format;
sufficiently robust;
adequate security (e.g. encryption);
sufficient bandwidth (data capacity);
growth potential;
automated report generation;
global coverage (could be achieved with more
than one technology).
The next ITU Word Radiocommunication Con-
ference will take place in 2012 (WRC-12) and the
main maritime radiocommunication items which
will be discussed are following (COMSAR 15,
2011):
to revise frequencies and channelling ar-
rangements of Appendix 17 to the Radio
Regulations, in accordance with Resolution 351
(Rev.WRC-07), in order to implement new digi-
tal technologies for the maritime mobile service;
and
to examine the frequency allocation requirements
with regard to operation of safety systems for
ships and ports and associated regulatory pro-
visions, in accordance with Resolution 357
(WRC-07).
From among other announcements concerning the
future GMDSS modification the following should be
given:
the new Arctic NAVAREAs/METAREAs are ex-
pected to be transitioned to Full Operational Ca-
pability (FOC) on 1 June 2011;
the new Arctic NAVAREAs/METAREAs are ex-
pected to be transitioned to Full Operational Ca-
pability (FOC) on 1 June 2011;
Inmarsat Global Limited (Inmarsat) has informed
of its intention to close the Inmarsat-B Service
from 31 December 2014;
the new Cospas-Sarsat MEOSAR system will be
probably full operational on 2018.
5 CONCLUSIONS
Twelve years have passed since the time when the
Global Maritime Distress and Safety System
(GMDSS) became introduced. Planning for the
GMDSS started more than 25 years ago, so elements
of it have been in place for many years.
There have been numerous advances in the use of
maritime radiocommunication to maritime safety,
security and environmental protection during this
period. But now there are some obsolete GMDSS
equipment and systems or the ones that have seldom
or never been used in practice.
On the other hand there are a lot of new digital
and information technologies.
Not only in the Author’s opinion, the time is ripe
to start the wide discussion on what the real condi-
tion and needs of the marine radiocommunication
are, in particular with reference to the current dis-
cussion on the e-navigation strategy.
During this work it is necessary first to identify
real user needs and secondly to realize that the mod-
ernization of the maritime radiocommunication
should not be driven by technical requirements. In
addition, it is necessary to ensure that man-machine-
interface and the human element will be taken into
account including the training of personnel.
The lessons learnt from the original development
and operation of GMDSS should be taken into ac-
count in the modification of GMDSS as well.
Furthermore a systematic process is needed to re-
view and modify the GMDSS to ensure it remains
modern and fully responsive to changes in require-
ments and evolutions of technology and it will meet
the expected e-navigation requirements.
For assuming this process a mechanism for con-
tinuous evolution of the GMDSS in a systematic
way should be created.
At the beginning, for synchronization of this
work a work plan for the process of the review and
modernization of the GMDSS should be established,
taking into account the above mentioned issues.
A framework document which defines timescales
of this work should be recognized as well.
And finally it should be noted that a key to the
success of the review and modernization process is
not only that the work is completed on time, but also
that it has the flexibility to implement changes ahead
of schedule.
In the above context further it should be noted
that the Sub-Committee on radiocommunications
and search and rescue (COMSAR) since it’s last ses-
sion in 2010 (COMSAR 14) has started work on is-
sue the Scoping Exercise to establish the need for a
review of the elements and procedures of the
GMDSS. Finish of this process is planed on COM-
SAR 16 in 2012 and it is expected that as the result
of this work a lot of answers will be given on the fu-
459
ture process of the review and modernization of the
GMDSS (COMSAR 14, COMSAR 15).
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